If you're a newly registered user here, you get put in the (wait for it) Newly Registered Users group. Right now, that group can only reply to topics - they can't start new ones. Sorry, but Chinese spam bots have made this change in policy necessary. If you're a legitimate user and want full posting rights, reply here and one of our administrators will get it for you ASAP.
FYI - For the time being, Gmail account registration is suspended. I'm sorry to do this, as I use Gmail myself, but an overwhelming number of spam accounts using Gmail has necessitated it. I'll be lifting the ban in about a month to see if the surge in Gmail spam account has subsided.